Marginal dietary zinc deprivation, such as those found in human populations in the US, result in clinically relevant zinc deficiencies during periods of rapid growth, such as infancy and adolescence. Nonhuman primates are similar to humans in showing an adolescent phase characterized by a growth spurt followed by sexual maturation and epiphyseal closure. In this experiment, we examined the effects of marginal zinc nutrition on adolescent development in a longitudinal study in female rhesus monkeys. A marginal dietary zinc deprivation was instituted in pre-pubertal rhesus monkeys by feeding a diet containing 25g Zn/g diet beginning at 18 months of age (prepubertal) and continuing to 42 months of age (sexual maturity). Controls (n=10/group) were fed 30 5g Zn/g diet. We found that growth rates of the zinc deprived monkeys fell behind those of controls during the growth spurt. Weight gain, body length and long bone length were all affected. Food intake (on a body weight basis) was not influenced. Bone mineralization as determined by dual energy atomic absorption x-ray scans was lower in the zinc deprived monkeys. Menarche occurred at the anticipated age, but fewer menstrual cycles were completed in the first months after menarche and the normal increase in nipple size was not observed in one zinc deprived monkey. Zinc-deprived monkeys showed decreased spontaneous activity and poorer performance of an attention task early in the deprivation period but behavior normalized after the onset of growth retardation. Zinc-deprived monkeys failed to show the normal shift in onset of the rest phase of the rest-activity cycle that normally occurs during adolescence. In summary, marginal zinc deprivation slowed adolescent growth and skeletal maturation, but did not prevent sexual maturation. Behavioral effects were seen primarily before the onset of the growth retardation. key words Nutrition, Bone, Reproductive system, Attention, Spontaneous motor activity, Puberty